Laser enrichment as described in U.S. Pat. No. 3,772,519 and U.S. patent application Ser. No. 328,954, filed Feb. 2, 1973 and Ser. No. 469,407, filed May 13, 1974 (incorporated herein by reference) typically employs a flowing uranium vapor which has been generated by electron beam techniques as the environment to which isotopically selective laser radiation is applied to produce excitation of a desired isotope type. Ultimately, ionization of the isotope type and separate collection thereof based upon the ionized charge is achieved in these techniques.
The electron beam vapor source has the advantage of limiting vaporization to a spot or line along the surface of a uranium melt typically contained within a crucible. Since high efficiency is desired for lower power consumption, as well as high evaporant flow rates with state of the art electron beam techniques, it has been suggested that a material be added to the uranium melt to impede the flow of convection currents normally encountered in the melt. Such an impedance barrier provides a great advantage in reducing heat loss through convection.